title: Water dynamics in hectorite clays: influence of temperature studied by coupling neutron spin echo and molecular dynamics.
abstract: Within the wider context of water behavior in soils, and with a particular emphasis on clays surrounding underground radioactive waste packages, we present here the translational dynamics of water in clays in low hydrated states as studied by coupling molecular dynamics (MD) simulations and quasielastic neutron scattering experiments by neutron spin echo (NSE). A natural montmorillonite clay of interest is modeled by a synthetic clay which allows us to understand the determining parameters from MD simulations by comparison with the experimental values. We focus on temperatures between 300 and 350 K, i.e., the range relevant to the highlighted application. The activation energy Ea experimentally determined is 6.6 kJ/mol higher than that for bulk water. Simulations are in good agreement with experiments for the relevant set of conditions, and they give more insight into the origin of the observed dynamics.
authors.affiliation: UPMC University Paris 06, UMR 7195, PECSA, F-75005 Paris, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Marry
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Dubois
authors.forename: Natalie
authors.initials: N
authors.lastname: Malikova
authors.forename: Serge
authors.initials: S
authors.lastname: Durand-Vidal
authors.forename: Stéphane
authors.initials: S
authors.lastname: Longeville
authors.forename: Josef
authors.initials: J
authors.lastname: Breu
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D057446:Hydrodynamics; D013058:Mass Spectrometry; D008958:Models, Molecular; D009502:Neutrons; D011835:Radiation Protection / Q000379:methods; D017640:Silicates / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D013696:Temperature
chemical_list: D000538:Aluminum Silicates; D017640:Silicates; D012987:Soil; C013547:hectorite; D000077215:Clay